The present invention relates to a process for preparing an aqueous polymer dispersion by free-radical emulsion polymerization of a monomer mixture which comprises N,N-diethylaminoethyl methacrylate, to the polymer dispersion obtainable by this process, and to the use thereof.
DE 1090381 describes a process for coating pharmaceutical forms with coating compositions soluble in the stomach. These comprise a copolymer of 20 to 80% of at least one amino ester of (meth)acrylic acid and 80 to 20% of a monomer which, as homopolymer, forms a water-insoluble polymer. Specific examples mentioned of suitable polymerizable amino esters are the esters of acrylic acid and (meth)acrylic acid with N,N-dimethylaminoethanol, N,N-diethylaminoethanol, N,N-dimethylaminopropanol and N-(hydroxyethyl)morpholine. Suitable comonomers mentioned are lower esters of acrylic acid and preferably of (meth)acrylic acid, such as ethyl acrylate, methyl, butyl and hexyl(meth)acrylates. Preparation takes place by solution polymerization in an organic solvent; no exemplary embodiment is indicated.
DE 1219175 describes a process for preparing veterinary medical active ingredient preparations which are protected from the effect of ruminal fluids of ruminants. For this purpose, these preparations are coated with copolymers which comprise as copolymerized units N,N-dialkylaminoalkyl(meth)acrylamides and a comonomer selected from (meth)acrylates, acrylonitrile and vinyl aromatic compounds. Copolymers based on N,N-dialkylaminoalkyl(meth)acrylates are regarded as disadvantageous according to this document because the ester group is prone to hydrolysis in a basic medium by contrast with the amide group.
DE 2135073 describes coating compositions for pharmaceutical forms which comprise an aqueous polymer dispersion, where the polymer is composed of 10 to 55% by weight of monomers having a carboxyl group and/or a monoalkyl- or dialkylaminoalkyl ester group. Besides a large number of others, diethylaminoethyl methacrylate (DEAEMA) is also mentioned as suitable monomer. Suitable comonomers mentioned are the lower esters of (meth)acrylic acid, preferably methyl methacrylate, (meth)acrylonitrile, vinyl aromatic compounds, vinyl chloride and vinyl acetate. Preparation takes place by aqueous emulsion polymerization, preferably by the emulsion feed process. No specific emulsion polymers based on DEAEMA are disclosed.
DE 2512238 teaches, for providing binders for pharmaceutical coatings with low residual monomer content, the use of a powder obtained by spray drying a polymer dispersion for preparing coating solutions for these pharmaceutical forms. Concerning the dispersions employed for the spray drying, reference is made to DE 1090381, DE 1219175 and DE 2135073.
DE 2838278 describes coatings for oral dosage forms for ruminants composed of    a) at least one film-forming polymer having at least one basic amino group and having a nitrogen content of from 3 to 14%, which is soluble within 24 hours in aqueous ruminal medium at a pH above 5.5, and    b) at least one hydrophobic substance which is dispersed in the polymer and is selected from C12-C32 fatty acids, Al salts of these fatty acids and/or polycarboxylic acids.
The coating is prepared by employing a solution in an organic solvent. Suitable polymers mentioned are a large number of nitrogen-containing homo- and copolymers, without entering into suitable processes for the preparation thereof. In this connection, a copolymer of 40% N,N-diethylaminoethyl methacrylate is mentioned in exemplary embodiment 29, but without indicating a process for its preparation.
GB 1324087 describes coating polymers for oral dosage forms for ruminants which comprise as copolymerized units    a) at least one N,N-dialkylaminoalkyl(meth)acrylate and    b) at least one ethylenically unsaturated compound selected from vinyl aromatic compounds and derivatives thereof, vinyl esters, esters of (meth)acrylic acid and acrylonitrile.
Disclosed as suitable monomers a) are N,N-dimethylaminoethyl methacrylate (DMAEMA) and tert-butylaminoethyl methacrylate (TBAEMA). Methyl methacrylate is regarded in particular as unsuitable as comonomer b) because it is prone to form coatings which are too brittle. Polymerization processes indicated as suitable are bulk, suspension, solution and emulsion polymerizations. The copolymers of the exemplary embodiments were prepared by solution polymerization.
DE 3426587 A1 describes a process for coating pharmaceutical forms by applying a film of a liquid, film-forming coating agent which comprises a dissolved polymer with tertiary ammonium salt side groups. These polymer solutions can be prepared inter alia by converting copolymers based on N,N-dialkylaminoalkyl(meth)acrylates with aqueous inorganic or organic acids into aqueous ammonium salt solutions.
DE 3049179 A1 is a branched application from DE 2512238 and relates to the use of a powder obtained by spray drying according to the teaching of the latter document, in the form of an aqueous suspension which additionally comprises a plasticizer, for producing coatings by thermal gelation.
EP 0058765 A2 describes coating compositions which are soluble or swellable in gastric fluid for pharmaceutical forms which comprise as binder an emulsion polymer based on N,N-dialkylaminoalkyl(meth)acrylates, there being located between the amino group and the (meth)acrylate group a branched alkylene or aralkylene group having at least three carbon atoms dispersed in a straight chain.
WO 2005/055986 and WO 2005/056619 describe polymers with pH-dependent swelling/dissolving behavior and the use thereof in pharmaceutical forms.
WO 00/05307 is concerned with the provision of coating agents and binders for pharmaceutical forms which comprise (meth)acrylate copolymers which include monomer residues with tertiary amino groups, the intention being that simple dry or aqueous further processing be possible. To this end, this document teaches a process in which (a) a copolymer of C1-C4 esters of (meth)acrylic acid and (meth)acrylate monomers which include tertiary ammonium groups, (b) a plasticizer and (c) an emulsifier with an HLB of at least 14 are blended together, and the coating agent or binder is prepared therefrom by melting, casting, spreading or spraying, where copolymer (a) is introduced in powder form with an average particle size of from 1 to 40 μm. The processability achieved in this case is ascribed to the provision of copolymer (a) in powder form with an extremely small particle size.
WO 02/067906 relates to coating agents and binders with improved water vapor permeability compared with those described in WO 00/05307. In this case, the coating agents and binders are prepared with a mixture which comprises (a) a copolymer of C1-C4 esters of (meth)acrylic acid and further (meth)acrylate monomers having functional tertiary ammonium groups in powder form with an average particle size of from 1 to 40 μm, (b) an emulsifier with an HLB of at least 14 and (c) a C1, —C18 monocarboxylic acid or a C12-C18 hydroxyl compound.
WO 2004/019918 describes coating agents and binders which correspond in terms of their composition to those described in WO 00/05307 and WO 02/067906.